It is known to selectively enable or disable a vehicle air bag or other occupant protection device based on the presence of an occupant in a seat. It has been proposed to place electrically conductive material in a vehicle seat to serve as an electrode for detecting the presence of an occupant in the seat. For example, U.S. Patent Application Publication No. 2009/0267622 A1, which is hereby incorporated herein by reference, describes a vehicle occupant detection system that determines the presence of an occupant based on the electrode's electrical characteristics. The electrical characteristics may be determined by coupling an excitation signal to the electrode to generate an electrode signal, and processing the electrode signal to determine an electrode signal magnitude that is indicative of an occupancy state.
The frequencies of excitation signals suggested for such occupant detection range from 1 kHz to 100 kHz, and higher. A sampling rate of ten or more times the excitation frequency is typically suggested to reliably detect the magnitude of such electrode signals. It will be appreciated that an analog-to-digital converter capable of sampling such electrode signals at the sample rates suggested are undesirably expensive, particularly when considered for use in a vehicle such as an automobile.